Radical and Ion

Radicals and ions are reactive species. Both are produced from a neutral atom or a molecule that is more stable than an ion or a radical.

Radical

Radical is a species (atom, molecule) with an unpaired electron. In other words, they have an open shell configuration, and because of this, radicals are highly unstable, which leads to a high reactivity. Therefore, they are short lived. When radicals collide with another species, they tend to react in a way that leads to pairing of their unpaired electron. They can do this by obtaining an atom from another molecule. That atom will give the radical an electron to pair with its unpaired electron. However, due to this another radical is formed (the species who donated the atom to the previous radical will become a radical now). Another way a radical can react is by combining with a compound containing a multiple bond to produce a new larger radical. When a covalent bond is homolysed (the two electrons participating to make the bond are divided equally to the two atoms so that one atom gets only one electron), radicals are formed. Energy must be supplied to cause homolysis of covalent bonds. This is done in two ways, by heating or by irradiating with light. For example, peroxides produce oxygen radicals when they are subjected to heat. Normally when radicals are formed, they undergo a chain of reactions producing more and more radical. A chain reaction of a radical can be divided into three parts as initiation, propagation and termination. To stop a radical reaction (termination), two radicals should be joined together to form a covalent bond back. Radical reactions are important in many industrial processes. Radicals are used to produce plastics or polymers such as polythene. They are also important for the combustion processes by which the fuels are converted to energy. In living systems, radicals are always produced as intermediates in metabolism. However, radicals are considered as harmful within living systems. They can cause aging, cancer, atherosclerosis, etc. Therefore, in terms of medicine, radicals are also important.

Ion

Ions are charged species with a positive or a negative charge. Positively charged ions are known as cations and negatively charged ions are known as anions. When forming a cation, an electron from the atom is giving out. When forming an anion, an electron is obtained to the atom. Therefore, in an ion there is a different number of electrons than the protons. Ions can have -1 or +1 charges, which we call as monovalent. Likewise, there are divalent, trivalent, etc charged ions. Since cations and anions have opposite charges, they are attracted to each other with electrostatic forces, forming ionic bonds. Cations are usually formed by metal atoms, and the anions are formed by nonmetal atoms. For example, Sodium is a group 1 metal, thus forms a +1 charged cation. Chlorine is a nonmetal and has the ability to form a -1 charged anion.

What is the difference between Radical and Ion? • Ion is a species which has obtained an extra electron or donated an electron out. Radical is a species with an unpaired electron. • Ions have a positive or a negative charge. Radicals can have a positive, negative charge or no charge.